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Date:   Fri, 31 Aug 2018 10:10:50 -0700
From:   Stephen Boyd <>
To:     "Zhu, Yi Xin" <>,
        Songjun Wu <>,,,
        Michael Turquette <>,, Rob Herring <>,
        Mark Rutland <>
Subject: Re: [PATCH v2 02/18] clk: intel: Add clock driver for Intel MIPS SoCs

Quoting Zhu, Yi Xin (2018-08-28 23:56:22)
> On 8/28/2018 3:09 AM, Stephen Boyd wrote:
> > Quoting yixin zhu (2018-08-08 01:52:20)
> >> On 8/8/2018 1:50 PM, Stephen Boyd wrote:
> >>>> +/* clock flags definition */
> >>>> +#define CLOCK_FLAG_VAL_INIT    BIT(16)
> >>>> +#define GATE_CLK_HW            BIT(17)
> >>>> +#define GATE_CLK_SW            BIT(18)
> >>>> +#define GATE_CLK_VT            BIT(19)
> >>> What does VT mean? Virtual?
> >> Yes. VT means virtual here.
> >> Will change to GATE_CLK_VIRT.
> >>
> > Is it a hardware concept? Or virtualization with hypervisor?
> Some peripheral drivers want to use same code cross platforms.
> But not all platforms provide HW gate clock.  So in this case, clock 
> driver creates
> a virtual gate clock to make it work if no HW gate clock in the SoC.

That's not how things are supposed to work. If a clk isn't there in the
hardware we don't make them up in software so that the consumer software
drivers can keep requesting clks on different platforms. On a different
platform, the driver needs to know that the clks aren't there with a
different compatible string.

> >
> >>>> +}
> >>>> +
> >>>> +CLK_OF_DECLARE(intel_grx500_cgu, "intel,grx500-cgu", grx500_clk_init);
> >>> Any reason a platform driver can't be used instead of CLK_OF_DECLARE()?
> >> It provides CPU clock which is used in early boot stage.
> >>
> > Ok. What is the CPU clock doing in early boot stage? Some sort of timer
> > frequency? If the driver can be split into two pieces, one to handle the
> > really early stuff that must be in place to get timers up and running
> > and the other to register the rest of the clks that aren't critical from
> > a regular platform driver it would be good. That's preferred model if
> > something is super critical.
> Yes, CPU clock is providing CPU frequency in the early boot stage.
> Will put the non-critical clocks in the platform driver.

Sure the CPU clock is handling frequency, but does that matter for early
boot to get going? If timers aren't involved here then it doesn't sound
like this needs CLK_OF_DECLARE.

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